The present invention relates generally to a method of driving a plasma display panel, particularly to a method of driving a surface-discharge type plasma display panel.
A surface-discharge type plasma display panel is formed by alternatively placing a plurality of maintaining electrodes X,Y on the inner surface of a single identical substrate.
However, in the above-described structure, since an electrode X and an electrode Y are situated adjacent to one another between two displaying lines, an electric potential difference occurs between two displaying lines during a sustain period. In order to prevent undesired panel discharge, it is necessary to enlarge a space between every two displaying lines. However, since a pitch between every two displaying lines has to be enlarged, it is difficult to produce a plasma display panel having a compact structure with a high precision.
In order to solve the above problem, there has been suggested an improved electrode arrangement as shown in FIG. 10. As shown in FIG. 10, maintaining electrodes X, Y are arranged in a manner such that their mutual positional relationship is alternatively changed from one displaying line L to another. Further, each maintaining electrode X receiving an identical drive signal is positioned between two adjacent maintaining electrodes Y (such as Y1 and Y2, Y3 and Y4) being driven selectively and successively. The maintaining electrodes X and maintaining electrodes Y are provided on the inner surface of a front substrate. Each of maintaining electrodes X and Y comprises a transparent electrode 4 consisting of a transparent electrically conductive film, and a bus electrode 3 (metal electrode) consisting of laminated metal layers for improving the electrical conductivity of the transparent electrode 4.
When such a surface-discharge type plasma display panel is driven, a unit displaying period is divided into an address period and a sustain period. During the address period, either a selective writing address method or a selective erasing address method is used, so that wall electric charges are accumulated in discharging cells (to be lighted) successively from one displaying line to another. During the sustain period as shown in FIG. 11, discharge maintaining pulses having the same phases are alternatively applied to maintaining electrodes X, Y on all the displaying lines, so as to effect a desired discharge emission.
However, with an electrode arrangement shown in FIG. 10 where each maintaining electrode X is positioned between two adjacent maintaining electrodes Y (for example, Y1 and Y2, Y3 and Y4), when discharge maintaining pulses IPx and IPy are applied to the maintaining electrodes (X,Y), an electric current IX.sub.1,2 (displacement current, discharging current) flowing through the maintaining electrode (X.sub.1,2) will become a value including currents IY.sub.1, IY.sub.2 flowing through adjacent maintaining electrodes Y.sub.1 and Y.sub.2. As a result, a peak electric current will be considerably large.
Consequently, if a voltage drop on a bus electrode 3 is large and a width of a bus electrode 3 is narrow, the plasma display panel will have a deteriorated displaying quality.
On the other hand, if a width W.sub.2 of a bus electrode 3 on a maintaining electrode X.sub.1,2 is larger than a width W.sub.1 of a bus electrode 3 on an adjacent maintaining electrode Y (Y1 or Y2), it is sure that a voltage drop on the bus electrode 3 on maintaining electrode X.sub.1,2 will be small. However, with a plasma display panel in which all the maintaining electrodes are positioned on an inner surface of a front substrate, there will be a problem that a numerical aperture is small and an emission efficiency is low due to a fact that light is obstructed by the bus electrodes 3.